1. Field of the Invention
The present invention relates to an uncooled optical semiconductor device which can accurately control the bias voltage of the electric field absorption type optical modulator so as to keep constant the average intensity of the optical modulated signal in a simple configuration.
2. Background Art
The amount of light absorbed by an electric field absorption type optical modulator varies depending on the temperature even when a voltage applied is constant. For this reason, an uncooled optical semiconductor device not subjected to cooling for keeping its temperature constant needs to adjust a bias voltage applied to the electric field absorption type optical modulator according to the temperature.
Conventional uncooled optical semiconductor devices predetermine a bias voltage to be applied to an electric field absorption type optical modulator for a certain temperature beforehand through testing or the like. The semiconductor devices perform control so that a bias voltage matches the temperature through a microcontroller or the like while monitoring the temperature using a temperature sensor (e.g., see Japanese Patent Laid-Open No. 2007-279406).
Furthermore, an optical semiconductor device is also proposed which detects a peak value of a light absorption current generated when an electric field absorption type optical modulator absorbs laser light and feeds back the peak value to a bias voltage applied to the electric field absorption type optical modulator (e.g., see Japanese Patent Laid-Open No. 10-117170).